In the processing of mineral-containing ores, it is necessary to separate undesirable minerals known as gangue (e.g., Al2O3, SiO2 and TiO2) from the desired minerals in ore (e.g., iron ore). One method of accomplishing this goal is to depress the flotation of a particular mineral during the normal flotation process. In mineral flotation systems, it is common to depress the gangue materials while floating the desirable mineral or minerals. In differential or reverse flotation systems, it is common to depress the desired mineral or minerals while floating the gangue. Depression is conventionally accomplished by the use of one or more depressing agents (also known as depressants) during the flotation step. The depressant, when added to the flotation system, exerts a specific action on the material to be depressed thereby preventing it from floating. The ability of the depressant to facilitate such separation is referred to as its selectivity, i.e., a more selective depressant achieves better separation of the gangue from the desired minerals.
In a typical ore flotation scheme, the ore is ground to a size sufficiently small to liberate the desired mineral or minerals from the gangue. An additional step in the flotation process involves the removal of the ultra-fine particles by desliming. Ultra-fine particles are generally defined as those less than 5 to 10 microns in diameter. The desliming process may be accompanied by or followed by a flocculation step or some other type of settling step such as the use of a cyclone separating device. This step is followed by a flotation step wherein gangue materials are separated from the desired mineral or minerals in the presence of collectors and/or frothers.
It has been conventional in many flotation systems to use naturally derived substances such as starches, dextrins and gums as depressants. In some countries, there is a prohibition against using substances such as starch which have food value in this type of commercial application.
Corn fiber is a low value byproduct of the corn milling process that is commonly blended with steep liquor and used as animal feed. The major components of corn fiber are cellulose, hemicellulose, protein, oil, lignin and starch. Hemicellulose is typically isolated from corn fiber by an alkaline hydrogen peroxide process (AHP). In AHP, corn fiber is mixed with alkaline solution and peroxide at high temperature. The resulting product contains a solid portion and a liquid portion, which contains the hemicellulose. The solid portion may be separated from the liquid portion, but separation can be cumbersome because the dissolved organic solid content is low and only from about 50-75% of the corn fiber dissolves in the reaction medium.